Generally, an epoxy resin has been used as base material and a phenol novolak or cresol novolak has been employed as curing agent for forming a protective film or smooth layer on a colored resin film formed on the surface of a glass plate or the like. Combination of such base material and curing agent, however, was usually poor in leveling qualities and tended to form pinholes or unevenness in the produced protective film or smooth layer.
In the course of studies on protective film or smooth layer for colored resin film, especially the one for color filter for liquid crystal displays, the present inventors found previously that a thin film with excellent leveling qualities and free of pinholes could be obtained from a phenol novolak and/or cresol novolak and an amino silane-modified product of glycidyl ether of phenol novolak and/or cresol novolak by dissolving them in an organic solvent, coating the solution on a substrate such as a glass plate, then drying and curing the coat (Japanese Patent Application Laid-Open (KOKAI) No. 63-77921 (1988)).
For obtaining the aminosilane-modified product, however, it is necessary to carry out the reaction at a high temperature ranging from 60.degree. to 140.degree. C., and also the aminosilicon used as modifier must be reacted almost 100%. Insufficient reaction results in the formation of fine silicon particles in he reaction system, and such fine silicon particles cause scattering of transmitted light to impair the function of color filter for liquid crystal displays.